A046260 Largest palindromic substring in 2^n.

1, 2, 4, 8, 6, 3, 6, 8, 6, 5, 4, 8, 9, 9, 8, 8, 55, 131, 262, 242, 8, 9, 9, 838, 777, 55, 88, 77, 545, 9, 737, 474, 949, 858, 717, 383, 767, 9, 77, 888, 777, 255552, 111, 222, 444, 888, 77, 3553, 767, 21312, 42624, 99, 737, 474, 9, 797, 575, 8558, 7117, 646, 606, 939

Offset: 0

Author

Patrick De Geest, Jun 15 1998

Keywords

• nonn
• base
• easy

Examples

			2^41 = 2199023{255552}.
		

Links

• Michael S. Branicky, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000079, A047813, A046268.

Programs

Python

def c(s): return s[0] != "0" and s == s[::-1]
def a(n):
    s = str(2**n)
    ss = (s[i:j] for i in range(len(s)) for j in range(i+1, len(s)+1))
    return max(int(w) for w in ss if c(w))
print([a(n) for n in range(62)]) # Michael S. Branicky, Sep 18 2022

Formula

a(n) = A047813(A000079(n)). - Michel Marcus, Sep 19 2022